no break for switch

[unlessgames]

I would expect a break in this code at the end of the when 0 block

fn := (x : number) =>
  switch x
    when 0
      num := 10
      switch num
        <? "number"
          return 0
    when 1
      return 1

but it's not there in the output.

It's different when the same thing is not inside the function

x := 1

switch x
  when 0
    num := 10
    switch num
      <? "number"
        return 0
  when 1
    return 1

Now the break is included (of course this code is not valid because of the top level return but yeah..)

Currently using noFallthroughCasesInSwitch in tsconfig.json to spot these errors.

[bbrk24]

It's omitting the break because it's the last statement of the function. If I add a call to an imaginary function g():

fn := (x : number) =>
  switch x
    when 0
      num := 10
      switch num
        <? "number"
          return 0
    when 1
      return 1
  g()

suddenly the break is there. Heck, the following statement doesn't even have to be substantial -- if I replace g() with ; in the above code it still emits the break.

[edemaine]

Right, it's clearly a bug in our code to detect whether a break is necessary (which we added to make eslint happier, IIRC).

[STRd6]

I think it's assuming that the inner switch is exhaustive when it's actually not. We should be able to do a bit better with it.

[bbrk24]

No, surprisingly -- if you add an else block that doesn't return, it still doesn't break.